A man who attended the Oakland Raiders game Thursday night was in serious condition after falling from a concourse at the O.co Coliseum, authorities said.

The man, whose name was not released, climbed over a wall on the concourse outside the third deck of the Coliseum, facing Oracle Arena, around 5:35 p.m., authorities said. The man hung briefly from a railing, then plunged to a concourse 30 feet below, Oakland police said.

Police believe the man climbed the wall intentionally but that the fall was an accident. The incident happened just as the Raiders' game against the Denver Broncos began.

The victim was taken to Highland Hospital in Oakland, where he was reported to be in serious condition. Police said he is expected to survive.